Polybutene-1 is a superior synthetic resin having excellent wear and creep resistances and high mechanical strength, but it has a relatively slow rate of crystallization and an extremely slow solid phase conversion from the metastable form to the stable form after melt molding. Accordingly, it is impossible to use polybutene-1 unless it is allowed to stand for about 7 days until the conversion from the metastable form to the stable form after molding has complete.
Therefore, some attempts have been heretofore made to improve the rate of crystal conversion of polybutene-1. For example, a method wherein butene-1 is random copolymerized with propylene is well known. [See APPLIED POLYMER SYMPOSIA, No. 11, 1-18, (1969).]